From: Jeffrey Hugo Date: Mon, 29 Aug 2016 20:38:52 +0000 (-0600) Subject: efi/libstub: Introduce ExitBootServices helper X-Git-Tag: v4.7.5~50 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=99d1ddb28b60297f7bb30ecb0e5837f00245c9a0;p=thirdparty%2Fkernel%2Fstable.git efi/libstub: Introduce ExitBootServices helper commit fc07716ba803483be91bc4b2344f9c84985e6f07 upstream. The spec allows ExitBootServices to fail with EFI_INVALID_PARAMETER if a race condition has occurred where the EFI has updated the memory map after the stub grabbed a reference to the map. The spec defines a retry proceedure with specific requirements to handle this scenario. This scenario was previously observed on x86 - commit d3768d885c6c ("x86, efi: retry ExitBootServices() on failure") but the current fix is not spec compliant and the scenario is now observed on the Qualcomm Technologies QDF2432 via the FDT stub which does not handle the error and thus causes boot failures. The user will notice the boot failure as the kernel is not executed and the system may drop back to a UEFI shell, but will be unresponsive to input and the system will require a power cycle to recover. Add a helper to the stub library that correctly adheres to the spec in the case of EFI_INVALID_PARAMETER from ExitBootServices and can be universally used across all stub implementations. Signed-off-by: Jeffrey Hugo Cc: Ard Biesheuvel Cc: Mark Rutland Cc: Leif Lindholm Cc: Ingo Molnar Signed-off-by: Matt Fleming Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c index 29368ac692213..aded106620204 100644 --- a/drivers/firmware/efi/libstub/efi-stub-helper.c +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c @@ -740,3 +740,76 @@ char *efi_convert_cmdline(efi_system_table_t *sys_table_arg, *cmd_line_len = options_bytes; return (char *)cmdline_addr; } + +/* + * Handle calling ExitBootServices according to the requirements set out by the + * spec. Obtains the current memory map, and returns that info after calling + * ExitBootServices. The client must specify a function to perform any + * processing of the memory map data prior to ExitBootServices. A client + * specific structure may be passed to the function via priv. The client + * function may be called multiple times. + */ +efi_status_t efi_exit_boot_services(efi_system_table_t *sys_table_arg, + void *handle, + struct efi_boot_memmap *map, + void *priv, + efi_exit_boot_map_processing priv_func) +{ + efi_status_t status; + + status = efi_get_memory_map(sys_table_arg, map); + + if (status != EFI_SUCCESS) + goto fail; + + status = priv_func(sys_table_arg, map, priv); + if (status != EFI_SUCCESS) + goto free_map; + + status = efi_call_early(exit_boot_services, handle, *map->key_ptr); + + if (status == EFI_INVALID_PARAMETER) { + /* + * The memory map changed between efi_get_memory_map() and + * exit_boot_services(). Per the UEFI Spec v2.6, Section 6.4: + * EFI_BOOT_SERVICES.ExitBootServices we need to get the + * updated map, and try again. The spec implies one retry + * should be sufficent, which is confirmed against the EDK2 + * implementation. Per the spec, we can only invoke + * get_memory_map() and exit_boot_services() - we cannot alloc + * so efi_get_memory_map() cannot be used, and we must reuse + * the buffer. For all practical purposes, the headroom in the + * buffer should account for any changes in the map so the call + * to get_memory_map() is expected to succeed here. + */ + *map->map_size = *map->buff_size; + status = efi_call_early(get_memory_map, + map->map_size, + *map->map, + map->key_ptr, + map->desc_size, + map->desc_ver); + + /* exit_boot_services() was called, thus cannot free */ + if (status != EFI_SUCCESS) + goto fail; + + status = priv_func(sys_table_arg, map, priv); + /* exit_boot_services() was called, thus cannot free */ + if (status != EFI_SUCCESS) + goto fail; + + status = efi_call_early(exit_boot_services, handle, *map->key_ptr); + } + + /* exit_boot_services() was called, thus cannot free */ + if (status != EFI_SUCCESS) + goto fail; + + return EFI_SUCCESS; + +free_map: + efi_call_early(free_pool, *map->map); +fail: + return status; +} diff --git a/include/linux/efi.h b/include/linux/efi.h index 4dd6fb50459b8..17fd2c5bf81f1 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1470,4 +1470,15 @@ efi_status_t efi_setup_gop(efi_system_table_t *sys_table_arg, unsigned long size); bool efi_runtime_disabled(void); + +typedef efi_status_t (*efi_exit_boot_map_processing)( + efi_system_table_t *sys_table_arg, + struct efi_boot_memmap *map, + void *priv); + +efi_status_t efi_exit_boot_services(efi_system_table_t *sys_table, + void *handle, + struct efi_boot_memmap *map, + void *priv, + efi_exit_boot_map_processing priv_func); #endif /* _LINUX_EFI_H */